Photodynamic therapy (“PDT”) has been used to treat various maladies and diseases. PDT often involves the use of a photosensitizing agent that is activated by electromagnetic radiation (e.g., light such as laser light). Therapeutic treatments of this type have been known for many years. For example, in some instances they have been applied to the treatment of localized cancer. There are photosensitizing drugs such as hematoporphyrin derivatives that have selective application to tumors. When activated by exposure to light, these drugs can cause cell necrosis. An example of this type of treatment is disclosed in U.S. Pat. No. 4,336,809.
PDT has also been used as a method for treating periodontal disease. When used with an appropriate photosensitizing compound, optical activation (e.g., by light or laser) irradiation is known to kill the type of bacteria that causes a number of oral or tooth-related diseases, including chronic periodontitis. This process is sometimes referred to as Photodynamic Disinfection (PDD).
The delivery of optical activation light in conjunction with PDT is often done with some type of optical fiber. As an example, U.S. Pat. No. 6,019,605 illustrates how an optical fiber is commonly used. In the patent, an optical fiber is inserted into the periodontal pocket near a tooth (see the '605 patent, FIG. 1, item 20). This type of fiber optic, light-delivery probe supplies light to a specific tissue area where treatment is needed. The way light is delivered or applied to the tissue depends on the optical characteristics and the shape of the tip at the very end of the fiber.
Whether or not optical fibers (or “fiber optic probes) are used in connection with PDT or in other kinds of medical applications where light is provided to an area or a cavity within the human body, it is sometimes desirable to have lateral dispersion or diffusion of light from the end of the probe. Normally, the majority or nearly all of the light emitted out from an end of the fiber is emitted in a narrow cone shape that is directional and coaxial with the end of the fiber. Therefore, it will be delivered essentially as a “spot” on a tissue area that generally corresponds to or is only slightly larger than the diameter of the fiber. In order to diffuse or disperse the light over a larger area, there have been instances where fiber optic probes have been designed with a “bead” element that caps the terminal end of the fiber to roughly emulate the effect created by a Fresnel lens. While this type of design can disperse light laterally relative to the fiber, it suffers drawbacks in several respects.
First, probes of this type enlarge the outer diameter beyond the normal diameter of the optical fiber. Typical optical fibers may have a diameter in the range of 300-600 microns. These small diameters are desirable because they are relatively non-invasive when used in conjunction with medical procedures. The small diameter of fiber optic probes becomes particularly important if the probe is to be positioned into a periodontal cavity between tooth and gums. It is obvious, therefore, that an enlarged probe tip is undesirable when used in applications of this type. Second, this type of tip may be susceptible to breaking away from the fiber, unless very secure modes of attachment are used. Typically, it is not desirable to have any part of a probe tip break off in a periodontal cavity or any other place inside the human body where it is desirable to deliver light.
The present invention is an improvement that addresses these and/or other kinds of design drawbacks of conventional probes.